The present invention relates to reclosable plastic bags and in particular to such bags which are designed for use as primary packaging. Reclosable bags are finding ever growing acceptance as primary packaging, particularly, as packaging for foodstuffs such as cereal, fresh vegetables, snacks and the like. Such bags provide the consumer with the ability to readily store, in a closed, if not sealed, package any unused portion of the packaged product even after the package is initially opened. To gain acceptance as a primary package for foodstuffs, it is virtually mandatory that the package exhibit some form of tamper evidence to protect the consumer and maintain the wholesomeness of the contained product. In addition, in many cases it is necessary that food product be hermetically packaged. This may readily be accomplished by forming a plastic bag of a film having the appropriate barrier properties. However, where the bag is provided with a zipper, a problem arises in properly sealing the bag at the opening to be closed by the zipper, since the zipper itself does not provide a hermetic seal.
In view of the above, it is the principle object of the present invention to provide a reclosable plastic bag which exhibits tamper evidence and which may be hermetically sealed.
A further object is to provide such a bag in which the zipper of the bag may readily be provided with a slider if desired.
In U.S. Pat. No. 5,023,122 a plastic film sheet for use in forming a reclosable container is disclosed. The plastic film sheet includes profiles and a line of tear perforations which penetrate the film sheet. A frangible cap strip overlies the perforations providing an impervious seal which prevents the passage of air and moisture through the perforations. The strip is weaker than the film so that the film will tear along the perforations and the cap strip will separate along its length with the tearing of the film.
The present invention makes use of a strip having the above described, capped perforations, or another form of weakening, in a unique bag configuration. Accordingly, in accordance with the present invention a bag is provided having front and rear walls joined along the bottom and sides and open at the top. A zipper is provided at the bag top having a first profile and a second profile, the profiles including interlocking elements designed to interlock with each other. Each of the profiles includes at least one flange, the one flange extending from below the profile interlocking element toward the bag interior. The flanges are of unequal size with the shorter flange being sealed directly to one of the bag walls. The longer flange is sealed to the other bag wall and to the one bag wall below the point at which the shorter flange is sealed to the one bag wall. A line of weakening, such as the above described capped line of perforations is provided in the longer flange between the locations at which it is sealed to the two walls. The capped line of perforations or other form of a line of weakening is such as to weaken the profile flange, so that it may be readily ruptured, without detracting from the barrier property of the profile flange until rupturing actually occurs.